The Minnesota Legislature will spend $18,000 on an outside attorney to defend its interests in a voter ID lawsuit.

House and Senate members of the Legislative Coordinating Commission adopted a resolution today to formally join the case, which was brought by opponents of a proposed requirement that all Minnesotans show photo identification in order to vote. The ACLU and other groups contend the constitutional amendment ballot question contains errors and omissions.

But Republicans who passed the amendment during the 2012 session want to make sure it remains on the statewide ballot in November. Sen. Michelle Benson, R-Ham Lake, said the intervention is an appropriate step.

“When the Legislature takes a strong position, we do have an inherent right to stand before the court and affirm that position,” Benson said.

The Minnesota House and Senate have gone to court many times before, but it might be the first time the Legislature as a whole has joined an existing lawsuit, according to Joel Michael, an attorney with the non-partisan House Research department.

“To my knowledge, the Legislature has never taken this exact action,” Michael said.

House Minority Leader Paul Thissen, DFL-Minneapolis, argued against the resolution. Thissen said the intervention was not only unprecedented, but an an unwise use of taxpayer money.

“We’re going to be paying more tax dollars to defend what we should have done right the first time, and we didn’t do it right the first time,” Thissen said.

The Minnesota Supreme Court is scheduled to hear arguments in the case on July 17.